Field of the Invention
The present invention relates to an overload prevention mechanism for a weighing apparatus. The overload prevention mechanism can prevent inclination of a weighing dish, reduce rattling in a rotational direction of the weighing dish, and thereby protect the highly precise electronic balance and the like from an instantaneous large load applied to a weighing dish thereof, besides be easily manufactured.
Description of the Related Art
Conventionally, an overload prevention mechanism (cushioning mechanism, shock absorber) has been also mounted in a weighing apparatus incorporated in a manufacturing line and the like, and a kind of overload prevention mechanism have realized omnidirectional release of overload (Patent Literature 1). A highly precise balance such as an electromagnetic-force-balancing electronic balance can measure a slight weight, for example, one several thousandths of a gram, one several-tens thousandth of a gram. In such balance, a mechanism for measuring material is configured very precisely. Accordingly, the mechanism may be broken due to a large load or instantaneous load.
In particular, in the case of a small-sized weighing apparatus, a weighing dish has been positioned in the vertical direction by a shaft of a load receiving part supporting the weighing dish at the position near the center of the weighing dish. Accordingly, even slight inclination of the shaft act on the weighing dish as more significant inclination. Also, the weighing dish is positioned in the rotational direction by receiving a pin which penetrates the shaft of the load receiving part with U-shaped groove at the portion near the center of the weighing dish. Accordingly, as with the inclination, rattling of the shaft appears at the end surface of the weighing dish as more significant rattling.
Such inclination and rattling in the rotational direction of the weighing dish were sometimes problematic in a weighing apparatus incorporated in equipment such as manufacturing line. In particular, this problem is more remarkable, for example, when a user uses the weighing apparatus with a long receiving jig added to the weighing dish.
As another conventional art, a cushioning device which is configured to be positioned in the vertical and rotational directions by three pins arranged at equal intervals in the circumferential direction and in which notches for receiving the pins are formed in a member serving as a weighing dish has been proposed (Patent Literature 2). However, as shown in FIGS. 1 and 4 of Patent Literature 2, it is necessary for the weighing dish of weighing apparatus to cut and form triangular pin positioning notches 23 and pin guiding grooves 24 continuous with the pin positioning notches 23 in the receiving member 20. As a result, manufacturing cost becomes expensive. In addition, driving the pin 32 into the pin hole requires man hours. Further, assembled weighing dish tends to incline due to precision and errors of the pin driving, or errors occurring in the pin hole and the pins 32, thereby making accurate weighing impossible.